During a pot experiment run at the greenhouse laboratory of University of Warmia and Mazury in Olsztyn (53^o46'26" N; 20^o29'30" E) in three series over 2002- -2005 on light and heavy soils, the process of competition between spring barley and field peas was investigated for three periods determined by the development rhythm of barley as single crop, i.e. during the stages of: seedling growth (Zadoks 10-13), tillering (25), stem elongation (32), heading (55) and ripening (87-91). The experiment was established according to the additive pattern in 4 repetitions. During the determined periods the yields of dry mass from different parts of plants (stems, leaves, heads, hulls and roots) were determined. The data was used for computation of crop growth rate. It was shown that joint cultivation of both species, as compared to single crop cultivation, from the very beginning of vegetation led to reduction of their overground and root mass. The process intensified with the passage of time. The negative influence of the added component was less limiting for the dry mass increase in stems but it was the most pronounced in the heads and hulls. The type of soil base had no influence on the accumulation of dry mass in the plants of spring barley and in the overground parts of field pea as opposed to its roots where a larger reduction in roots biomass was recorded in heavy soil. In case of mixture crop, the biomass accumulation rate decrease was recorded for both species over the entire vegetation period.

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